1. Field of the Invention
This invention pertains to a liquid sight monitor for monitoring the presence of liquid in an accompanying liquid system and/or the level of liquid in such a liquid system, which liquid may be of a type that is highly corrosive to the materials previously employed in liquid sight monitors.
2. Description of the Prior Art
Liquid sight monitors include both sight flow indicators and liquid level gauges. As a sight flow indicator, a liquid sight monitor is employed as a bypass section or as an in-line section of a passive or flowing liquid system to show an observer whether liquid is present in the system. As a liquid level gauge, a sight monitor is employed in a vertical bypass connection to show an observer the standing liquid level of the system to which it is connected.
Typically, a transparent glass tube is used in the sight monitor to provide viewing of the liquid systems. Such tube can be shielded by a metallic or plastic sleeve with an elongate slit to permit viewing of the glass tube. Also, a concentric tube can be provided around the tube for providing an annular space between the tubes that helps keep the viewing tube clear. As desired, such space can be, environmentally left alone, or the space may be evacuated or filled with a gas, and may be separately cooled or heated differently from the monitored system. Examples of sight monitors are shown in U.S. Pat. No. 3,381,976, Goodson et al, issued May 7, 1968; U.S. Pat. No. 4,345,468, Jackson, issued Aug. 24, 1982 and U.S. Pat. application Ser. No. 785,782, Jobe, filed Oct. 8, 1985, and now abandoned all of which are commonly assigned and incorporated herein by reference for all purposes.
The connectors of liquid sight monitors previously employed with the glass tubes just described have included metallic or plastic flanges accepting inserts for connecting the glass tube or tubes to the flanges and to the liquid system tank, pipe or the like. The connecting inserts have heretofore been made of fluoroplastics or other firm body material for accepting O-rings of neoprene or similar resilient material or have included integral ridges dimensioned to provide the required resiliency for sealing against the glass tube or tubes. The tubes themselves have desirably been made of borosilicate glass or other similar materials.
Although certainly suitable for many if not most applications, such prior art sight monitors do include some form of glass for the viewing element. Glass is inert to many liquids, but not all. For example, hydrofluoric acid will etch and eventually dissolve glass. A glass viewing element also requires a connecting insert with or without O-rings, as briefly described above, to allow it to be connected in place with a metallic or plastic flange end. These elements also are subject ot corrosive attack by some fluids. In addition, they age over a period of time and are subject to becoming fouled by grime and other constituent components existing in some liquid systems. This means that the system frequently has to be shut down and the sight monitor disassembled and cleared. Parts thereof are in need of fairly frequent replacement, as well.
Therefore, it is a feature of the present invention to provide an improved viewing element for a liquid sight monitor that resists corrosive attack by liquids that attack glass and not requiring other connecting component parts for joining the viewing element to a connecting flange, thereby avoiding other potentially corrosive attacks.
It is another feature of the present invention to provide an improved liquid sight monitor in a translucent thermoplastic embodiment having a self-mounting configuration.